Proximal tibial morphology and risk of posterior tibial cortex impingement in patients with AA-sized Oxford unicompartmental knee arthroplasty tibial implants

• Published in: Journal of orthopaedic surgery and research Vol. 15; no. 1; p. 380
• Main Authors: Charng, Jiun-Ran, Chen, Alvin Chao-Yu, Chan, Yi-Shen, Hsu, Kuo Yao, Wu, Chen-Te
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 03.09.2020; BioMed Central; BMC
• Subjects: Aged; Arthritis; Arthroplasty (knee); Arthroplasty, Replacement, Knee - adverse effects; Arthroplasty, Replacement, Knee - methods; Asian population; Cortex; Female; Fractures; Humans; Joint surgery; Keel impingement; Knee; Knee - anatomy & histology; Knee - physiopathology; Knee Prosthesis; Knee replacement arthroplasty; Ligaments; Male; Middle Aged; Morphology; Orthopedics; Osteoarthritis; Osteoarthritis, Knee - surgery; Oxford; Postoperative Complications - etiology; Postoperative Complications - prevention & control; Proximal tibial; Surgical techniques; Tibia; Tibia - anatomy & histology; Tibia - injuries; Tibia - physiopathology; Transplants & implants; Unicompartmental knee; White people; Keel impingement; Proximal tibial; Asian population; Oxford; Morphology; Unicompartmental knee
• ISSN: 1749-799X; 1749-799X
• DOI: 10.1186/s13018-020-01900-6

In cases of Oxford unicompartmental knee arthroplasty (UKA), an increase in anteroposterior and medial-lateral length is usually disproportional when comparing AA and A-sized tibial components. Asynchronous increments may cause tibial keel impingement leading to complications. Radiographic measurements were performed in five patients with AA-sized tibial implants. The posterior cortex of proximal tibia had two angles recorded as ∠ M1 and ∠ M2. The minimum distance between the tibial component keel and outer margin of the posterior tibial cortex (mDKC) was measured, and the correlation between the preoperative posterior slope angle (PSA), ∠ M1, and mDKC was analyzed. All patients showed an acceptable component positioning. Only one patient had an mDKC of < 4 mm that fulfilled the criteria for the posterior tibial cortex at risk. The patient had an increased PSA and ∠ M1 compared to other patients. A negative correlation was found between preoperative PSA and mDKC (r = - 0.935, p = 0.0193); and ∠ M1 and mDKC (r = - 0.969, p = 0.0032). However, no stem tip pain, periprosthetic fracture, or component loosening were observed. The distance between the tibial keel and posterior tibial cortex was reduced in AA-sized patients with a large PSA and ∠M1; therefore, the risk of the tibial cortex injury should be considered.